Goldsack suffered the injury at training last week prior to Collingwood’s 69-point win over Essendon.
The 28-year-old also missed the previous match against Melbourne due to illness.
“Unfortunately we were expecting Tyson Goldsack to play last week but he hurt himself at training, I think on the Saturday,” Magpies football director Neil Balme told the club’s website.
“He fractured his thumb.
“It was fairly clean. He’s had surgery on it. They put a plate in and he’s certainly medium term.
“We’re hoping he might be able to come back within four weeks but he may be longer than that.”
The Pies play the Eagles at Domain Stadium on Sunday afternoon.